Transfer Switch - Basic question

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  #1  
Old 12-14-11, 07:28 PM
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Transfer Switch - Basic question

From my main panel, I need to remove all circuits that will be generator-backup'ed and bring them to my transfer switch.

Transfer switch is 60A 120/240

My main panel uses fuses.



What would you do to bring power to the transfer switch?
A - 240V 30A pull-out block

B - Two 30A fuses on different legs



How would you re-wire the backup'ed circuits to start from the transfer switch?

A - Splice from within the main panel and leave through a knock-out to the transfer switch?

B - Completely pulled out of the main panel to the transfer switch?



Lastly, would you bond the ground of the transfer switch at:
A - Transfer switch ground to main panel ground bus

B - Join the ground cable of the transfer switch to the ground cable of the main panel with a split nut (cable that goes to electrode)


In your answer, specify if it's a preference, or if it's code.

Thanks
 
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  #2  
Old 12-15-11, 05:29 PM
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I know you have a 60 amp transfer switch and I know you have fuses and not breakers, but I don't know the amperage output of your generator. From your description, I am assuming the transfer switch has a small panel built into it. Ideally you'll want a normal power input to the transfer switch equivalent to the generator power input to the transfer switch. Assuming your generator has a 60 amp output to the 60 amp transfer switch, you'll want a 60 amp normal power to the transfer switch from your main panel as well. Do you have a 2 pole 60 amp fusible pullout?

What would you do to bring power to the transfer switch?

A - 240V 30A pull-out block

B - Two 30A fuses on different legs
My assumption of a 60 amp generator output may be wrong. If it has a 30 amp output, I'd use a 240V 30A fusible pullout for normal power to the transfer switch.

How would you re-wire the backup'ed circuits to start from the transfer switch?


A - Splice from within the main panel and leave through a knock-out to the transfer switch?

B - Completely pulled out of the main panel to the transfer switch?
I would remove the NM cables from the main panel and extend them to the transfer switch panel and then use K.O. closers on the extra openings at the main panel.

Lastly, would you bond the ground of the transfer switch at:

A - Transfer switch ground to main panel ground bus

B - Join the ground cable of the transfer switch to the ground cable of the main panel with a split nut (cable that goes to electrode)
I would include a grounding conductor with the normal power feed to the transfer switch and terminate it at the transfer switch on a ground bar or in a lug bolted to the transfer switch box.

In your answer, specify if it's a preference, or if it's code.
My answers are based upon a standby generator with automatic transfer switch and are my preference. They should also meet requirements of the NEC, but you are in Canada. I cannot speak for Canadadian codes, but I believe they are similar.
 
  #3  
Old 12-15-11, 06:20 PM
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Yes the cec is nearly identical especially on elementary codes such as those in my case.

The generator outputs 240v 30a on two 120v 30a hot legs. It gives the capacity of using up 60a at 120v if evenly balanced on the two legs.

The transfer panel has 3-pole main breakers for two hot legs and a neutral all 30a. The neural breaker is only there for the option of a generator with neutral already bonded. So since it's floating neutral we can pretend it's a 2-pole.


The fuses are on my main electrical panel. So to equivocate the generator output, I believe I should use a 2-pole 30a 240v pullout fuse to bring utility power to my manual transfer panel, which as you assumed is a breaker panel with two sets of main breakers to switch between utility and generator.

Thanks for the recommendations.

Oh and here's the diagram of my transfer switch


Yeah quality sucks. Worst part is, that's from the PDF document on the manufacturer's website. It looks like they created it on paper then scanned it

And it's even worse on the paper itself that came in the box.

Now that I analyze that diagram again after sleeping on it, I realize that I don't need a ground wire from the main electrical panel to the transfer switch. The bond occurs in the main electrical panel. A heavy gauge neutral conductor goes from the electrical panel to the transfer switch neutral bus. That neutral conductor wire is already bonded in the electrical panel.


Also, on the diagram they didn't include what looks like the ground bus that's located at the bottom middle of the panel, running horizontally. I'm assuming it's the ground bus because it's connected to the metal case of the panel (Not plastic isolator). But I don't see how the return grounds connected to the bus would bond with the neutral. The neutral bus isn't grounded to the panel.
 

Last edited by insthink; 12-15-11 at 07:03 PM.
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